Ecmweb 14026 Thinkstockphotos 485981637webversion 1
Ecmweb 14026 Thinkstockphotos 485981637webversion 1
Ecmweb 14026 Thinkstockphotos 485981637webversion 1
Ecmweb 14026 Thinkstockphotos 485981637webversion 1
Ecmweb 14026 Thinkstockphotos 485981637webversion 1

Tip of the Week: Starting Motors Under Load, or Not

May 22, 2017
Before trying to start a motor under load, you should verify that it can be done.

Some motors can start under load, and some can’t. Where a motor is coupled to the load without an intervening clutch system on the load end, assume the motor cannot start under load unless you verify it can. And that generally means it needs to be a Design D motor, which has “extra high” starting torque.

Photo credit: branex/iStock/Thinkstock

You’ll find Design D motors in punch presses and other forming tools. You’ll also find them in cranes, elevators, and hoists. They typically aren’t used in most other applications.

Pumps are ubiquitous in process plants and other industrial facilities. These are typically powered by Design B motors. The starting torque of Design B motors is considered “medium.”

Something that sometimes happens in plants is an operator tries to start a pump that is “dead headed.” The downstream valve is closed so the pump is (typically) trying to compress a liquid rather than push it through the piping. Because the Design B motor lacks the torque to start under such a load, it will generate considerable heat trying. Then it will blow its overloads. You’ll need to wait a while, maybe a couple of hours, before a restart attempt.

Before starting a Design B motor, ensure it’s not under load. If it runs a pump, ensure the pump isn’t valved out. This doesn’t mean you simply open a closed valve; verify with operations that valve operation is permitted and that flow through the system by operating the pump is also permitted.

Be sure you follow all operating procedures, including any established division of labor rules.

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.

Voice your opinion!

To join the conversation, and become an exclusive member of EC&M, create an account today!

Sponsored Recommendations

Electrical Conduit Comparison Chart

CHAMPION FIBERGLASS electrical conduit is a lightweight, durable option that provides lasting savings when compared to other materials. Compare electrical conduit types including...

Don't Let Burn-Through Threaten Another Data Center or Utility Project

Get the No Burn-Through Elbow eGuide to learn many reasons why Champion Fiberglass elbows will enhance your data center and utility projects today.

Considerations for Direct Burial Conduit

Installation type plays a key role in the type of conduit selected for electrical systems in industrial construction projects. Above ground, below ground, direct buried, encased...

How to Calculate Labor Costs

Most important to accurately estimating labor costs is knowing the approximate hours required for project completion. Learn how to calculate electrical labor cost.